A sourdough process based on fermented chickpea extract as leavening and anti-staling agent for improving the quality of gluten-free breads

Abstract

The use of a sourdough (SD) preparation based on a fermented chickpea extract (FCE) starter as a leavening and anti-staling agent in gluten-free breads was explored in this study. The FCE starter was prepared by a submerged fermentation (at 37 °C for 15 h) of coarsely ground chickpeas and the gluten-free bread formulations, based on rice and corn flours, were made using a rice sourdough produced with the FCE starter as additional leavening agent; the FCE-SD breads and samples containing merely baker's yeast as microbial leavener (control) were both prepared at three different levels of added water, i.e., 85, 92 and 100% (flour weight basis). The loaf specific volume significantly (p < 0.05) increased with sourdough inclusion into batters and by increasing the amount of added water. Moreover, inclusion of sourdough into the gluten-free formulations resulted in a finer porous crumb macrostructure and a lower crust moisture content than control breads. Upon bread storage (25 °C for 5 days), water migration from crumb to crust was noted. Staling events were also monitored by compression testing and differential scanning calorimetry, showing an increase in crumb firmness and the apparent melting enthalpy (ΔH) of retrograded amylopectin during bread storage; the values for both parameters decreased with inclusion of FCE-SD and with higher amounts of added water into the gluten-free formulations. Kinetic data in modelling crumb firmness and ΔH values by linear regression analysis and the Avrami equation, respectively, revealed a slower staling rate for breads with sourdough, compared to control formulations; moreover, with increasing level of added water to the batter, the firming rate was reduced, while the amylopectin retrogradation was enhanced. Finally, in vitro enzymatic starch digestibility of the crumb was lower for staled breads stored for 5 days, compared to fresh products, while there was no pronounced effect by sourdough inclusion. Overall, the incorporation of FCE-SD into gluten-free bread formulations seems to be a promising alternative for improving quality and extending the shelf life of gluten-free baked products.

Keywords: Amylopectin retrogradation; Avrami equation; Bread in vitro enzymatic digestibility; Bread shelf life; Bread staling; Bread texture.